The present invention relates to an apparatus for manufacturing a filtering medium in sheet form.
Filters for fluids which comprise a structure for supporting and containing a filtering mass, through which the fluid to be filtered is passed so as to flow from a region connected to an inlet connector to a region connected to an outlet connector, are conventionally widely used in various fields of technology.
The filtering medium used most frequently is constituted by a sheet of paper, which is inserted in the filter after being folded and rolled up according to various methods; a filtering medium in sheet form has been recently proposed which comprises regions having a differentiated filtration degree and offers numerous advantages.
In one embodiment of the filtering medium, for example, the medium comprises longitudinal bands which alternately have a different filtration degree.
It is also known that paper-making technology entails the presence of at least two kinds of continuous machine.
A first kind of machine, known as flat-screen machine, comprises a head box which conveys natural or synthetic fibers in an aqueous suspension over a conveyor constituted by a supporting screen, which moves above suction boxes suitable to collect the water that passes through the screen, so as to form on the screen a fiber mat, known as web, which is then gradually dried until it assumes the conventionally sheet-like configuration.
A second type of machine, known as cylinder machine, comprises a container which contains a fibrous suspension in water and a hollow cylinder which is partially immersed in the suspension and covered with a wire mesh or equivalent material and rotates about a horizontal axis.
During rotation, the fibers cling to the surface of the wire mesh and are picked up by a conveyor constituted by a supporting felt, which is arranged tangent to the cylinder and is pushed against it by a presser roller.
There are machines which have a cylinder with a uniformly transparent wire mesh and machines in which the cylinder has a wire mesh with closed regions where no fibers deposit on the supporting felt.